Can your users choose one of those subscription plans, or one or more of them? You’ve got an individual <select> for each one which suggests they can select one, two or three of them, but if you only want them to select one, surely it should be a single <select> with three options? If you can choose multiple ones, I’d have thought three check-boxes would be more logical.
I can’t immediately see why it wouldn’t store the $fees in that final query. What is the value of $fees just before you run the query? What do you get if you var_dump($_POST)?